It is known to convert cyanuric chloride obtained in the form of vapor by trimerization of cyanogen chloride directly or via liquid cyanuric chloride into solid cyanuric chloride in finely particulate form:
The deposition of pulverulent cyanuric chloride by desublimation of cyanuric chloride in vapor form can be carried out in externally cooled chambers or by introducing cyanuric chloride vapor together with an inert gas and/or an inert cooling liquid vaporizing during the deposition process, into a deposition chamber--see for example DE-PS 12 66 308 and U.S. Pat. No. 4,591,493. In the preparation of finely particulate cyanuric chloride from liquid cyanuric chloride the latter is injected through a nozzle into a deposition chamber and cooled with cycled inert cooling gases or by indirect cooling in the deposition chamber until the spray droplets deposit in crystalline form--see for example DE 28 43 379. A common feature of these processes is a considerable technical expenditure on deposition chambers and devices for recycling and purifying the process gases and waste gases.
In the previously evaluated processes as well as processes based on the same principles, cyanuric chloride is always obtained in finely particulate form, in general having a maximum grain diameter of substantially less than 250 .mu.m. Such finely particulate products are of course advantageous as regards their high reactivity, but have a number of disadvantages that make a different product form desirable for many purposes.
The handling, including conveyance, storage and metering, of finely particulate cyanuric chloride presents special problems since finely particulate substances usually lead to the formation of dusts that have corrosive and irritant properties and require suction purification equipment. In addition cyanuric chloride is sensitive to hydrolysis, and the resultant hydrolysis products can contaminate not only the cyanuric chloride itself but also following product produced therefrom. Finely particulate cyanuric chloride is particularly susceptible to hydrolysis on account of its large surface area. As a result solid deposits are also readily formed in the dust removal equipment and dust-conveying lines. Technically complicated and costly measures and/or equipment are necessary in order to avoid and eliminate resultant malfunctions.
A further disadvantage of finely particulate cyanuric chloride is the unsatisfactory flowability. Although the latter can admittedly be improved by adding flow auxiliaries, for example silicic acids, nevertheless the flow auxiliary reduces the product purity of the cyanuric chloride and possibly also of products prepared therefrom. According to EP-A 0 416 584 the flowability of solid cyanuric chloride prepared by desublimation or spray crystallization can also be improved without adding a flow auxiliary by a shear treatment of the cyanuric chloride in a kneader or mixer, especially at 60 to 120.degree. C.; the finely pulverulent nature of the cyanuric chloride is not however affected by this process, for the mean grain size of typical embodiments is in the range from about 10 to 40 .mu.m.
As well as the finely particulate form, cyanuric chloride is also commercially available in liquid form. The preparation of cyanuric chloride in liquid form is known for example from DE-PS 23 32 636. The liquid cyanuric chloride product form requires however storage and transporting vessels and containers that can be heated above the melting point of cyanuric chloride. Although such equipment is economical for users having a large and regular demand for cyanuric chloride, this is not the case however for users having a small and/or irregular demand for cyanuric chloride.